diff --git a/README.md b/README.md
index 5c5c8d36..4efa9939 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,7 @@ check the output of `xmodmap -pke`
 
 If you can't find what you need, consult
 [linux/input-event-codes.h](https://github.com/torvalds/linux/blob/master/include/uapi/linux/input-event-codes.h)
+for KEY and BTN names
 
 - Mouse buttons `BTN_LEFT` `BTN_RIGHT` `BTN_MIDDLE` `BTN_SIDE`
 - Multimedia keys `KEY_NEXTSONG` `KEY_PLAYPAUSE` ...
diff --git a/keymapper/dev/injector.py b/keymapper/dev/injector.py
index 52306d21..8be8ad84 100644
--- a/keymapper/dev/injector.py
+++ b/keymapper/dev/injector.py
@@ -37,7 +37,7 @@ from keymapper.state import system_mapping
 from keymapper.dev.keycode_mapper import handle_keycode, \
     should_map_event_as_btn
 from keymapper.dev.ev_abs_mapper import ev_abs_mapper, JOYSTICK
-from keymapper.dev.macros import parse
+from keymapper.dev.macros import parse, is_this_a_macro
 
 
 DEV_NAME = 'key-mapper'
@@ -101,12 +101,38 @@ class KeycodeInjector:
         self.mapping = mapping
         self._process = None
         self._msg_pipe = multiprocessing.Pipe()
+        self._code_to_code = self._map_codes_to_codes()
+        self.stopped = False
 
-        # some EV_ABS mapping stuff
+        # when moving the joystick and then staying at a position, no
+        # events will be written anymore. Remember the last value the
+        # joystick reported, because it is still remaining at that
+        # position.
         self.abs_state = [0, 0, 0, 0]
 
+    def _map_codes_to_codes(self):
+        """To quickly get target keycodes during operation."""
+        _code_to_code = {}
+        for (ev_type, keycode), output in self.mapping:
+            if is_this_a_macro(output):
+                continue
+
+            target_keycode = system_mapping.get(output)
+            if target_keycode is None:
+                logger.error('Don\'t know what %s is', output)
+                continue
+
+            _code_to_code[keycode] = target_keycode
+        return _code_to_code
+
     def start_injecting(self):
         """Start injecting keycodes."""
+        if self.stopped or self._process is not None:
+            # So that there is less concern about integrity when putting
+            # stuff into self. Each injector object can only be
+            # started once.
+            raise Exception('Please construct a new injector instead')
+
         self._process = multiprocessing.Process(target=self._start_injecting)
         self._process.start()
 
@@ -172,11 +198,16 @@ class KeycodeInjector:
 
         return device, abs_to_rel
 
-    def _modify_capabilities(self, input_device, abs_to_rel):
-        """Adds all keycode into a copy of a devices capabilities.
+    def _modify_capabilities(self, macros, input_device, abs_to_rel):
+        """Adds all used keycodes into a copy of a devices capabilities.
+
+        A device with those capabilities can do exactly the stuff it needs
+        to perform all mappings and macros.
 
         Prameters
         ---------
+        macros : dict
+            maping of int to _Macro
         input_device : evdev.InputDevice
         abs_to_rel : bool
             if ABS capabilities should be removed in favor of REL
@@ -187,20 +218,21 @@ class KeycodeInjector:
         # to act like the device.
         capabilities = input_device.capabilities(absinfo=False)
 
+        if len(self._code_to_code) > 0 or len(macros) > 0:
+            if capabilities.get(EV_KEY) is None:
+                capabilities[EV_KEY] = []
+
         # Furthermore, support all injected keycodes
-        if len(self.mapping) > 0 and capabilities.get(ecodes.EV_KEY) is None:
-            capabilities[ecodes.EV_KEY] = []
-
-        for (ev_type, keycode), character in self.mapping:
-            if not should_map_event_as_btn(ev_type, keycode):
-                continue
-
-            keycode = system_mapping.get(character)
-            if keycode is not None:
+        for keycode in self._code_to_code.values():
+            if keycode not in capabilities[EV_KEY]:
                 capabilities[EV_KEY].append(keycode)
 
+        # and all keycodes that are injected by macros
+        for macro in macros.values():
+            capabilities[EV_KEY] += list(macro.get_capabilities())
+
         if abs_to_rel:
-            del capabilities[ecodes.EV_ABS]
+            del capabilities[EV_ABS]
             # those are the requirements to recognize it as mouse
             # on my system. REL_X and REL_Y are of course required to
             # accept the events that the mouse-movement-mapper writes.
@@ -209,11 +241,11 @@ class KeycodeInjector:
                 evdev.ecodes.REL_Y,
                 evdev.ecodes.REL_WHEEL,
             ]
-            if capabilities.get(ecodes.EV_KEY) is None:
-                capabilities[ecodes.EV_KEY] = []
+            if capabilities.get(EV_KEY) is None:
+                capabilities[EV_KEY] = []
             # for reasons I don't know, it is also required to have
             # any keyboard button in capabilities.
-            capabilities[ecodes.EV_KEY].append(ecodes.KEY_0)
+            capabilities[EV_KEY].append(ecodes.KEY_0)
 
         # just like what python-evdev does in from_device
         if ecodes.EV_SYN in capabilities:
@@ -253,32 +285,44 @@ class KeycodeInjector:
 
         # Watch over each one of the potentially multiple devices per hardware
         for path in paths:
-            input_device, abs_to_rel = self._prepare_device(path)
-            if input_device is None:
+            source, abs_to_rel = self._prepare_device(path)
+            if source is None:
                 continue
 
+            # each device parses the macros with a different handler
+            logger.debug('Parsing macros for %s', path)
+            macros = {}
+            for (ev_type, keycode), output in self.mapping:
+                if is_this_a_macro(output):
+                    macros[keycode] = parse(output)
+                    continue
+
             # certain capabilities can have side effects apparently. with an
             # EV_ABS capability, EV_REL won't move the mouse pointer anymore.
             # so don't merge all InputDevices into one UInput device.
             uinput = evdev.UInput(
                 name=f'{DEV_NAME} {self.device}',
                 phys=DEV_NAME,
-                events=self._modify_capabilities(input_device, abs_to_rel)
+                events=self._modify_capabilities(macros, source, abs_to_rel)
             )
 
+            def handler(*args, uinput=uinput):
+                # this ensures that the right uinput is used for macro_write,
+                # because this is within a loop
+                self._macro_write(*args, uinput)
+
+            for macro in macros.values():
+                macro.set_handler(handler)
+
             # keycode injection
-            coroutine = self._keycode_loop(input_device, uinput, abs_to_rel)
+            coroutine = self._keycode_loop(macros, source, uinput, abs_to_rel)
             coroutines.append(coroutine)
 
             # mouse movement injection
             if abs_to_rel:
                 self.abs_state[0] = 0
                 self.abs_state[1] = 0
-                coroutine = ev_abs_mapper(
-                    self.abs_state,
-                    input_device,
-                    uinput
-                )
+                coroutine = ev_abs_mapper(self.abs_state, source, uinput)
                 coroutines.append(coroutine)
 
         if len(coroutines) == 0:
@@ -296,59 +340,34 @@ class KeycodeInjector:
         if len(coroutines) > 0:
             logger.debug('asyncio coroutines ended')
 
-    def _macro_write(self, character, value, uinput):
+    def _macro_write(self, code, value, uinput):
         """Handler for macros."""
-        keycode = system_mapping[character]
-        logger.spam(
-            'macro writes code:%s value:%d char:%s',
-            keycode, value, character
-        )
-        uinput.write(EV_KEY, keycode, value)
+        logger.spam('macro writes code:%s value:%d', code, value)
+        uinput.write(EV_KEY, code, value)
         uinput.syn()
 
-    async def _keycode_loop(self, device, uinput, abs_to_rel):
+    async def _keycode_loop(self, macros, source, uinput, abs_to_rel):
         """Inject keycodes for one of the virtual devices.
 
         Can be stopped by stopping the asyncio loop.
 
         Parameters
         ----------
-        device : evdev.InputDevice
+        macros : int -> _Macro
+            macro with a handler that writes to the provided uinput
+        source : evdev.InputDevice
             where to read keycodes from
         uinput : evdev.UInput
             where to write keycodes to
         abs_to_rel : bool
             if joystick events should be mapped to mouse movements
         """
-        # efficiently figure out the target keycode without taking
-        # extra steps.
-        code_code_mapping = {}
-
-        # Parse all macros beforehand
-        logger.debug('Parsing macros')
-        macros = {}
-        for (ev_type, keycode), output in self.mapping:
-            if '(' in output and ')' in output and len(output) >= 4:
-                # probably a macro
-                macros[keycode] = parse(
-                    output,
-                    lambda *args: self._macro_write(*args, uinput)
-                )
-                continue
-
-            target_keycode = system_mapping.get(output)
-            if target_keycode is None:
-                logger.error('Don\'t know what %s is', output)
-                continue
-
-            code_code_mapping[keycode] = target_keycode
-
         logger.debug(
             'Started injecting into %s, fd %s',
             uinput.device.path, uinput.fd
         )
 
-        async for event in device.async_read_loop():
+        async for event in source.async_read_loop():
             if abs_to_rel and event.type == EV_ABS and event.code in JOYSTICK:
                 if event.code == evdev.ecodes.ABS_X:
                     self.abs_state[0] = event.value
@@ -361,7 +380,7 @@ class KeycodeInjector:
                 continue
 
             if should_map_event_as_btn(event.type, event.code):
-                handle_keycode(code_code_mapping, macros, event, uinput)
+                handle_keycode(self._code_to_code, macros, event, uinput)
                 continue
 
             # forward the rest
@@ -369,9 +388,6 @@ class KeycodeInjector:
             # this already includes SYN events, so need to syn here again
             continue
 
-        # this should only ever happen in tests to avoid blocking them
-        # forever, as soon as all events are consumed. In normal operation
-        # there is no end to the events.
         logger.error(
             'The injector for "%s" stopped early',
             uinput.device.path
@@ -382,3 +398,4 @@ class KeycodeInjector:
         """Stop injecting keycodes."""
         logger.info('Stopping injecting keycodes for device "%s"', self.device)
         self._msg_pipe[1].send(CLOSE)
+        self.stopped = True
diff --git a/keymapper/dev/keycode_mapper.py b/keymapper/dev/keycode_mapper.py
index 2dd8ad91..a212cc95 100644
--- a/keymapper/dev/keycode_mapper.py
+++ b/keymapper/dev/keycode_mapper.py
@@ -52,12 +52,12 @@ def should_map_event_as_btn(type, code):
     return False
 
 
-def handle_keycode(code_code_mapping, macros, event, uinput):
+def handle_keycode(_code_to_code, macros, event, uinput):
     """Write the mapped keycode or forward unmapped ones.
 
     Parameters
     ----------
-    code_code_mapping : dict
+    _code_to_code : dict
         mapping of linux-keycode to linux-keycode.
     macros : dict
         mapping of linux-keycode to _Macro objects
@@ -84,8 +84,8 @@ def handle_keycode(code_code_mapping, macros, event, uinput):
         asyncio.ensure_future(macro.run())
         return
 
-    if input_keycode in code_code_mapping:
-        target_keycode = code_code_mapping[input_keycode]
+    if input_keycode in _code_to_code:
+        target_keycode = _code_to_code[input_keycode]
         target_type = evdev.events.EV_KEY
         logger.spam(
             'got code:%s value:%s event:%s, maps to EV_KEY:%s',
diff --git a/keymapper/dev/macros.py b/keymapper/dev/macros.py
index 0b0fb426..72d8acae 100644
--- a/keymapper/dev/macros.py
+++ b/keymapper/dev/macros.py
@@ -40,9 +40,9 @@ import re
 
 from keymapper.logger import logger
 from keymapper.config import config
+from keymapper.state import system_mapping
 
 
-# for debugging purposes
 MODIFIER = 1
 CHILD_MACRO = 2
 SLEEP = 3
@@ -51,17 +51,19 @@ KEYSTROKE = 5
 DEBUG = 6
 
 
+def is_this_a_macro(output):
+    """Figure out if this is a macro."""
+    if '(' in output and ')' in output and len(output) >= 4:
+        return True
+
+
 class _Macro:
     """Supports chaining and preparing actions."""
-    def __init__(self, handler, depth, code):
+    def __init__(self, depth, code):
         """Create a macro instance that can be populated with tasks.
 
         Parameters
         ----------
-        handler : func
-            A function that accepts keycodes as the first parameter and the
-            key-press state as the second. 1 for down and 0 for up. The
-            macro will write to this function once executed with `.run()`.
         depth : int
             0 for the outermost parent macro, 1 or greater for child macros,
             like the second argument of repeat.
@@ -69,13 +71,42 @@ class _Macro:
             The original parsed code, for logging purposes.
         """
         self.tasks = []
-        self.handler = handler
+        self.handler = lambda *args: logger.error('No handler set')
         self.depth = depth
         self.code = code
 
+        # all required capabilities, without those of child macros
+        self.capabilities = set()
+
+    def get_capabilities(self):
+        """Resolve all capabilities of the macro and those of its children."""
+        capabilities = self.capabilities.copy()
+        for task_type, task in self.tasks:
+            if task_type == CHILD_MACRO:
+                capabilities.update(task.get_capabilities())
+        return capabilities
+
+    def set_handler(self, handler):
+        """Set the handler function.
+
+        Parameters
+        ----------
+        handler : func
+            A function that accepts keycodes as the first parameter and the
+            key-press state as the second. 1 for down and 0 for up. The
+            macro will write to this function once executed with `.run()`.
+        """
+        self.handler = handler
+        for task_type, task in self.tasks:
+            if task_type == CHILD_MACRO:
+                task.set_handler(handler)
+
     async def run(self):
         """Run the macro."""
-        for _, task in self.tasks:
+        for task_type, task in self.tasks:
+            if task_type == CHILD_MACRO:
+                task = task.run
+
             coroutine = task()
             if asyncio.iscoroutine(coroutine):
                 await coroutine
@@ -88,11 +119,19 @@ class _Macro:
         modifier : str
         macro : _Macro
         """
-        self.tasks.append((MODIFIER, lambda: self.handler(modifier, 1)))
+        modifier = str(modifier)
+        code = system_mapping.get(modifier)
+
+        if code is None:
+            raise KeyError(f'Unknown modifier "{modifier}"')
+
+        self.capabilities.add(code)
+
+        self.tasks.append((MODIFIER, lambda: self.handler(code, 1)))
         self.add_keycode_pause()
-        self.tasks.append((CHILD_MACRO, macro.run))
+        self.tasks.append((CHILD_MACRO, macro))
         self.add_keycode_pause()
-        self.tasks.append((MODIFIER, lambda: self.handler(modifier, 0)))
+        self.tasks.append((MODIFIER, lambda: self.handler(code, 0)))
         self.add_keycode_pause()
         return self
 
@@ -104,8 +143,9 @@ class _Macro:
         repeats : int
         macro : _Macro
         """
+        repeats = int(repeats)
         for _ in range(repeats):
-            self.tasks.append((CHILD_MACRO, macro.run))
+            self.tasks.append((CHILD_MACRO, macro))
         return self
 
     def add_keycode_pause(self):
@@ -119,14 +159,23 @@ class _Macro:
 
     def keycode(self, character):
         """Write the character."""
-        self.tasks.append((KEYSTROKE, lambda: self.handler(character, 1)))
+        character = str(character)
+        code = system_mapping.get(character)
+
+        if code is None:
+            raise KeyError(f'Unknown key "{character}"')
+
+        self.capabilities.add(code)
+
+        self.tasks.append((KEYSTROKE, lambda: self.handler(code, 1)))
         self.add_keycode_pause()
-        self.tasks.append((KEYSTROKE, lambda: self.handler(character, 0)))
+        self.tasks.append((KEYSTROKE, lambda: self.handler(code, 0)))
         self.add_keycode_pause()
         return self
 
     def wait(self, sleeptime):
         """Wait time in milliseconds."""
+        sleeptime = int(sleeptime)
         sleeptime /= 1000
 
         async def sleep():
@@ -191,15 +240,13 @@ def _count_brackets(macro):
     return position
 
 
-def _parse_recurse(macro, handler, macro_instance=None, depth=0):
+def _parse_recurse(macro, macro_instance=None, depth=0):
     """Handle a subset of the macro, e.g. one parameter or function call.
 
     Parameters
     ----------
     macro : string
         Just like parse
-    handler : function
-        passed to _Macro constructors
     macro_instance : _Macro or None
         A macro instance to add tasks to
     depth : int
@@ -211,11 +258,10 @@ def _parse_recurse(macro, handler, macro_instance=None, depth=0):
     # If this gets more complicated than that I'd rather make a macro
     # editor GUI and store them as json.
     assert isinstance(macro, str)
-    assert callable(handler)
     assert isinstance(depth, int)
 
     if macro_instance is None:
-        macro_instance = _Macro(handler, depth, macro)
+        macro_instance = _Macro(depth, macro)
     else:
         assert isinstance(macro_instance, _Macro)
 
@@ -247,7 +293,7 @@ def _parse_recurse(macro, handler, macro_instance=None, depth=0):
         logger.spam('%scalls %s with %s', space, call, string_params)
         # evaluate the params
         params = [
-            _parse_recurse(param.strip(), handler, None, depth + 1)
+            _parse_recurse(param.strip(), None, depth + 1)
             for param in string_params
         ]
 
@@ -258,7 +304,7 @@ def _parse_recurse(macro, handler, macro_instance=None, depth=0):
         if len(macro) > position and macro[position] == '.':
             chain = macro[position + 1:]
             logger.spam('%sfollowed by %s', space, chain)
-            _parse_recurse(chain, handler, macro_instance, depth)
+            _parse_recurse(chain, macro_instance, depth)
 
         return macro_instance
 
@@ -271,7 +317,7 @@ def _parse_recurse(macro, handler, macro_instance=None, depth=0):
     return macro
 
 
-def parse(macro, handler):
+def parse(macro):
     """parse and generate a _Macro that can be run as often as you want.
 
     Parameters
@@ -280,17 +326,13 @@ def parse(macro, handler):
         "r(3, k(a).w(10))"
         "r(2, k(a).k(-)).k(b)"
         "w(1000).m(Shift_L, r(2, k(a))).w(10, 20).k(b)"
-    handler : func
-        A function that accepts keycodes as the first parameter and the
-        key-press state as the second. 1 for down and 0 for up. The
-        macro will write to this function once executed with `.run()`.
     """
     # whitespaces, tabs, newlines and such don't serve a purpose. make
     # the log output clearer and the parsing easier.
     macro = re.sub(r'\s', '', macro)
     logger.spam('preparing macro %s for later execution', macro)
     try:
-        return _parse_recurse(macro, handler)
+        return _parse_recurse(macro)
     except Exception as error:
         logger.error('Failed to parse macro "%s": %s', macro, error)
         return None
diff --git a/keymapper/state.py b/keymapper/state.py
index f2cf1bd6..455594a0 100644
--- a/keymapper/state.py
+++ b/keymapper/state.py
@@ -34,32 +34,52 @@ from keymapper.mapping import Mapping
 XKB_KEYCODE_OFFSET = 8
 
 
-def populate_system_mapping():
-    """Get a mapping of all available names to their keycodes."""
-    mapping = {}
+class SystemMapping:
+    """Stores information about all available keycodes."""
+    def __init__(self):
+        """Construct the system_mapping."""
+        self._mapping = {}
+        self.populate()
 
-    xmodmap = subprocess.check_output(['xmodmap', '-pke']).decode() + '\n'
-    mappings = re.findall(r'(\d+) = (.+)\n', xmodmap)
-    for keycode, names in mappings:
-        # there might be multiple, like:
-        # keycode  64 = Alt_L Meta_L Alt_L Meta_L
-        # keycode 204 = NoSymbol Alt_L NoSymbol Alt_L
-        # only the first column is relevant. The others can be achieved
-        # by using a modifier button and the mapped key
-        name = names.split()[0]
-        mapping[name] = int(keycode) - XKB_KEYCODE_OFFSET
+    def populate(self):
+        """Get a mapping of all available names to their keycodes."""
+        self.clear()
+        xmodmap = subprocess.check_output(['xmodmap', '-pke']).decode() + '\n'
+        mappings = re.findall(r'(\d+) = (.+)\n', xmodmap)
+        for keycode, names in mappings:
+            # there might be multiple, like:
+            # keycode  64 = Alt_L Meta_L Alt_L Meta_L
+            # keycode 204 = NoSymbol Alt_L NoSymbol Alt_L
+            # Alt_L should map to code 64. Writing code 204 only works
+            # if a modifier is applied at the same time. So take the first
+            # one.
+            name = names.split()[0]
+            self._set(name, int(keycode) - XKB_KEYCODE_OFFSET)
 
-    for name, ecode in evdev.ecodes.ecodes.items():
-        mapping[name] = ecode
+        for keycode, names in mappings:
+            # but since KP may be mapped like KP_Home KP_7 KP_Home KP_7,
+            # make another pass and add all of them if they don't already
+            # exist. don't overwrite any keycodes.
+            for name in names.split():
+                if self.get(name) is None:
+                    self._set(name, int(keycode) - XKB_KEYCODE_OFFSET)
 
-    return mapping
+        for name, ecode in evdev.ecodes.ecodes.items():
+            self._set(name, ecode)
 
+    def _set(self, name, code):
+        """Map name to code."""
+        self._mapping[str(name).lower()] = code
 
-def clear_system_mapping():
-    """Remove all mapped keys. Only needed for tests."""
-    keys = list(system_mapping.keys())
-    for key in keys:
-        del system_mapping[key]
+    def get(self, name):
+        """Return the code mapped to the key."""
+        return self._mapping.get(str(name).lower())
+
+    def clear(self):
+        """Remove all mapped keys. Only needed for tests."""
+        keys = list(self._mapping.keys())
+        for key in keys:
+            del self._mapping[key]
 
 
 # one mapping object for the whole application that holds all
@@ -67,7 +87,7 @@ def clear_system_mapping():
 custom_mapping = Mapping()
 
 # this mapping represents the xmodmap output, which stays constant
-system_mapping = populate_system_mapping()
+system_mapping = SystemMapping()
 
 # permissions for files created in /usr
 _PERMISSIONS = stat.S_IREAD | stat.S_IWRITE | stat.S_IRGRP | stat.S_IROTH
diff --git a/tests/testcases/test_daemon.py b/tests/testcases/test_daemon.py
index 7ff6b9d0..9d0bd7e5 100644
--- a/tests/testcases/test_daemon.py
+++ b/tests/testcases/test_daemon.py
@@ -30,8 +30,7 @@ import gi
 gi.require_version('Gtk', '3.0')
 from gi.repository import Gtk
 
-from keymapper.state import custom_mapping, system_mapping, \
-    clear_system_mapping
+from keymapper.state import custom_mapping, system_mapping
 from keymapper.config import config
 from keymapper.daemon import Daemon, get_dbus_interface, BUS_NAME
 
@@ -78,6 +77,7 @@ class TestDaemon(unittest.TestCase):
             self.daemon = None
         evdev.InputDevice.grab = self.grab
         config.clear_config()
+        system_mapping.populate()
 
     def test_daemon(self):
         keycode_from_1 = 9
@@ -87,9 +87,9 @@ class TestDaemon(unittest.TestCase):
 
         custom_mapping.change((EV_KEY, keycode_from_1), 'a')
         custom_mapping.change((EV_KEY, keycode_from_2), 'b')
-        clear_system_mapping()
-        system_mapping['a'] = keycode_to_1
-        system_mapping['b'] = keycode_to_2
+        system_mapping.clear()
+        system_mapping._set('a', keycode_to_1)
+        system_mapping._set('b', keycode_to_2)
 
         preset = 'foo'
 
diff --git a/tests/testcases/test_injector.py b/tests/testcases/test_injector.py
index e0427bfb..c64a90f3 100644
--- a/tests/testcases/test_injector.py
+++ b/tests/testcases/test_injector.py
@@ -29,8 +29,7 @@ from evdev.ecodes import EV_REL, EV_KEY, EV_ABS, ABS_HAT0X
 from keymapper.dev.injector import is_numlock_on, toggle_numlock, \
     ensure_numlock, KeycodeInjector
 from keymapper.dev.keycode_mapper import handle_keycode
-from keymapper.state import custom_mapping, system_mapping, \
-    clear_system_mapping
+from keymapper.state import custom_mapping, system_mapping
 from keymapper.mapping import Mapping
 from keymapper.config import config
 from keymapper.dev.macros import parse
@@ -67,6 +66,7 @@ class TestInjector(unittest.TestCase):
             del pending_events[key]
         clear_write_history()
         custom_mapping.empty()
+        system_mapping.populate()
 
     def test_modify_capabilities(self):
         class FakeDevice:
@@ -80,21 +80,34 @@ class TestInjector(unittest.TestCase):
         mapping = Mapping()
         mapping.change((EV_KEY, 80), 'a')
 
-        # going to be ignored
+        macro_code = 'r(2, m(sHiFt_l, r(2, k(1).k(2))))'
+        macro = parse(macro_code)
+
+        mapping.change((EV_KEY, 60), macro_code)
+
+        # going to be ignored, because EV_REL cannot be mapped, that's
+        # mouse movements.
         mapping.change((EV_REL, 1234), 'b')
 
-        maps_to = system_mapping['a']
+        a = system_mapping.get('a')
+        shift_l = system_mapping.get('ShIfT_L')
+        one = system_mapping.get(1)
+        two = system_mapping.get('2')
 
         self.injector = KeycodeInjector('foo', mapping)
         fake_device = FakeDevice()
         capabilities = self.injector._modify_capabilities(
+            {60: macro},
             fake_device,
             abs_to_rel=False
         )
 
         self.assertIn(EV_KEY, capabilities)
         keys = capabilities[EV_KEY]
-        self.assertEqual(keys[0], maps_to)
+        self.assertIn(a, keys)
+        self.assertIn(one, keys)
+        self.assertIn(two, keys)
+        self.assertIn(shift_l, keys)
 
         self.assertNotIn(evdev.ecodes.EV_SYN, capabilities)
         self.assertNotIn(evdev.ecodes.EV_FF, capabilities)
@@ -154,7 +167,11 @@ class TestInjector(unittest.TestCase):
         device, abs_to_rel = self.injector._prepare_device(path)
         self.assertTrue(abs_to_rel)
 
-        capabilities = self.injector._modify_capabilities(device, abs_to_rel)
+        capabilities = self.injector._modify_capabilities(
+            {},
+            device,
+            abs_to_rel
+        )
         self.assertNotIn(evdev.ecodes.EV_ABS, capabilities)
         self.assertIn(evdev.ecodes.EV_REL, capabilities)
 
@@ -269,7 +286,7 @@ class TestInjector(unittest.TestCase):
         self.assertAlmostEqual(history[-2][2], -1)
 
     def test_handle_keycode(self):
-        code_code_mapping = {
+        _code_to_code = {
             1: 101,
             2: 102
         }
@@ -287,9 +304,9 @@ class TestInjector(unittest.TestCase):
 
         EV_KEY = evdev.ecodes.EV_KEY
 
-        handle_keycode(code_code_mapping, {}, Event(EV_KEY, 1, 1), uinput)
-        handle_keycode(code_code_mapping, {}, Event(EV_KEY, 3, 1), uinput)
-        handle_keycode(code_code_mapping, {}, Event(EV_KEY, 2, 1), uinput)
+        handle_keycode(_code_to_code, {}, Event(EV_KEY, 1, 1), uinput)
+        handle_keycode(_code_to_code, {}, Event(EV_KEY, 3, 1), uinput)
+        handle_keycode(_code_to_code, {}, Event(EV_KEY, 2, 1), uinput)
 
         self.assertEqual(len(history), 3)
         self.assertEqual(history[0], (EV_KEY, 101, 1))
@@ -299,18 +316,19 @@ class TestInjector(unittest.TestCase):
     def test_handle_keycode_macro(self):
         history = []
 
-        macro_mapping = {
-            1: parse('k(a)', lambda *args: history.append(args)),
-            2: parse('r(5, k(b))', lambda *args: history.append(args))
-        }
-
         code_a = 100
         code_b = 101
-        system_mapping['a'] = code_a
-        system_mapping['b'] = code_b
-        clear_system_mapping()
+        system_mapping.clear()
+        system_mapping._set('a', code_a)
+        system_mapping._set('b', code_b)
 
-        EV_KEY = evdev.ecodes.EV_KEY
+        macro_mapping = {
+            1: parse('k(a)'),
+            2: parse('r(5, k(b))')
+        }
+
+        macro_mapping[1].set_handler(lambda *args: history.append(args))
+        macro_mapping[2].set_handler(lambda *args: history.append(args))
 
         handle_keycode({}, macro_mapping, Event(EV_KEY, 1, 1), None)
         handle_keycode({}, macro_mapping, Event(EV_KEY, 2, 1), None)
@@ -326,10 +344,10 @@ class TestInjector(unittest.TestCase):
 
         # 6 keycodes written, with down and up events
         self.assertEqual(len(history), 12)
-        self.assertIn(('a', 1), history)
-        self.assertIn(('a', 0), history)
-        self.assertIn(('b', 1), history)
-        self.assertIn(('b', 0), history)
+        self.assertIn((code_a, 1), history)
+        self.assertIn((code_a, 0), history)
+        self.assertIn((code_b, 1), history)
+        self.assertIn((code_b, 0), history)
 
     def test_injector(self):
         custom_mapping.change((EV_KEY, 8), 'k(KEY_Q).k(w)')
@@ -338,13 +356,13 @@ class TestInjector(unittest.TestCase):
         input_b = 10
         custom_mapping.change((EV_KEY, input_b), 'b')
 
-        clear_system_mapping()
+        system_mapping.clear()
         code_a = 100
         code_q = 101
         code_w = 102
-        system_mapping['a'] = code_a
-        system_mapping['KEY_Q'] = code_q
-        system_mapping['w'] = code_w
+        system_mapping._set('a', code_a)
+        system_mapping._set('key_q', code_q)
+        system_mapping._set('w', code_w)
 
         # the second arg of those event objects is 8 lower than the
         # keycode used in X and in the mappings
diff --git a/tests/testcases/test_integration.py b/tests/testcases/test_integration.py
index 5716fda7..52897806 100644
--- a/tests/testcases/test_integration.py
+++ b/tests/testcases/test_integration.py
@@ -35,8 +35,7 @@ import shutil
 gi.require_version('Gtk', '3.0')
 from gi.repository import Gtk
 
-from keymapper.state import custom_mapping, system_mapping, \
-    clear_system_mapping
+from keymapper.state import custom_mapping, system_mapping
 from keymapper.paths import CONFIG, get_config_path
 from keymapper.config import config
 from keymapper.dev.reader import keycode_reader
@@ -110,6 +109,7 @@ class TestIntegration(unittest.TestCase):
         gtk_iteration()
         shutil.rmtree('/tmp/key-mapper-test')
         clear_write_history()
+        system_mapping.populate()
 
     def get_rows(self):
         return self.window.get('key_list').get_children()
@@ -428,8 +428,8 @@ class TestIntegration(unittest.TestCase):
         keycode_to = 200
 
         self.change_empty_row(keycode_from, 'a')
-        clear_system_mapping()
-        system_mapping['a'] = keycode_to
+        system_mapping.clear()
+        system_mapping._set('a', keycode_to)
 
         pending_events['device 2'] = [
             Event(evdev.events.EV_KEY, keycode_from, 1),
@@ -465,8 +465,8 @@ class TestIntegration(unittest.TestCase):
         keycode_to = 90
 
         self.change_empty_row(keycode_from, 't')
-        clear_system_mapping()
-        system_mapping['t'] = keycode_to
+        system_mapping.clear()
+        system_mapping._set('t', keycode_to)
 
         # not all of those events should be processed, since that takes some
         # time due to time.sleep in the fakes and the injection is stopped.
diff --git a/tests/testcases/test_macros.py b/tests/testcases/test_macros.py
index 7a6bcb2f..de476e10 100644
--- a/tests/testcases/test_macros.py
+++ b/tests/testcases/test_macros.py
@@ -25,6 +25,7 @@ import asyncio
 
 from keymapper.dev.macros import parse, _Macro
 from keymapper.config import config
+from keymapper.state import system_mapping
 
 
 class TestMacros(unittest.TestCase):
@@ -35,38 +36,70 @@ class TestMacros(unittest.TestCase):
     def tearDown(self):
         self.result = []
 
-    def handler(self, char, value):
-        """Where macros should write characters to."""
-        self.result.append((char, value))
+    def handler(self, code, value):
+        """Where macros should write codes to."""
+        self.result.append((code, value))
+
+    def test_set_handler(self):
+        macro = parse('r(1, r(1, k(1)))')
+        one_code = system_mapping.get('1')
+        self.assertSetEqual(macro.get_capabilities(), {one_code})
+
+        self.loop.run_until_complete(macro.run())
+        self.assertListEqual(self.result, [])
+
+        macro.set_handler(self.handler)
+        self.loop.run_until_complete(macro.run())
+        self.assertListEqual(self.result, [(one_code, 1), (one_code, 0)])
 
     def test_0(self):
-        self.loop.run_until_complete(parse('k(1)', self.handler).run())
-        self.assertListEqual(self.result, [(1, 1), (1, 0)])
+        macro = parse('k(1)')
+        macro.set_handler(self.handler)
+        one_code = system_mapping.get('1')
+        self.assertSetEqual(macro.get_capabilities(), {one_code})
+
+        self.loop.run_until_complete(macro.run())
+        self.assertListEqual(self.result, [(one_code, 1), (one_code, 0)])
 
     def test_1(self):
-        macro = 'k(1).k(a).k(3)'
-        self.loop.run_until_complete(parse(macro, self.handler).run())
+        macro = parse('k(1).k(a).k(3)')
+        macro.set_handler(self.handler)
+        self.assertSetEqual(macro.get_capabilities(), {
+            system_mapping.get('1'),
+            system_mapping.get('a'),
+            system_mapping.get('3')
+        })
+
+        self.loop.run_until_complete(macro.run())
         self.assertListEqual(self.result, [
-            (1, 1), (1, 0),
-            ('a', 1), ('a', 0),
-            (3, 1), (3, 0),
+            (system_mapping.get('1'), 1), (system_mapping.get('1'), 0),
+            (system_mapping.get('a'), 1), (system_mapping.get('a'), 0),
+            (system_mapping.get('3'), 1), (system_mapping.get('3'), 0),
         ])
     
     def test_2(self):
         start = time.time()
         repeats = 20
-        macro = f'r({repeats}, k(k))'
-        self.loop.run_until_complete(parse(macro, self.handler).run())
+
+        macro = parse(f'r({repeats}, k(k))')
+        macro.set_handler(self.handler)
+        k_code = system_mapping.get('k')
+        self.assertSetEqual(macro.get_capabilities(), {k_code})
+
+        self.loop.run_until_complete(macro.run())
         keystroke_sleep = config.get('macros.keystroke_sleep_ms')
         sleep_time = 2 * repeats * keystroke_sleep / 1000
         self.assertGreater(time.time() - start, sleep_time * 0.9)
         self.assertLess(time.time() - start, sleep_time * 1.1)
-        self.assertListEqual(self.result, [('k', 1), ('k', 0)] * repeats)
+        self.assertListEqual(self.result, [(k_code, 1), (k_code, 0)] * repeats)
 
     def test_3(self):
         start = time.time()
-        macro = 'r(3, k(m).w(100))'
-        self.loop.run_until_complete(parse(macro, self.handler).run())
+        macro = parse('r(3, k(m).w(100))')
+        macro.set_handler(self.handler)
+        m_code = system_mapping.get('m')
+        self.assertSetEqual(macro.get_capabilities(), {m_code})
+        self.loop.run_until_complete(macro.run())
 
         keystroke_time = 6 * config.get('macros.keystroke_sleep_ms')
         total_time = keystroke_time + 300
@@ -75,26 +108,42 @@ class TestMacros(unittest.TestCase):
         self.assertGreater(time.time() - start, total_time * 0.9)
         self.assertLess(time.time() - start, total_time * 1.1)
         self.assertListEqual(self.result, [
-            ('m', 1), ('m', 0),
-            ('m', 1), ('m', 0),
-            ('m', 1), ('m', 0),
+            (m_code, 1), (m_code, 0),
+            (m_code, 1), (m_code, 0),
+            (m_code, 1), (m_code, 0),
         ])
 
     def test_4(self):
-        macro = '  r(2,\nk(\nr ).k(-\n )).k(m)  '
-        self.loop.run_until_complete(parse(macro, self.handler).run())
+        macro = parse('  r(2,\nk(\nr ).k(minus\n )).k(m)  ')
+        macro.set_handler(self.handler)
+
+        r = system_mapping.get('r')
+        minus = system_mapping.get('minus')
+        m = system_mapping.get('m')
+
+        self.assertSetEqual(macro.get_capabilities(), {r, minus, m})
+
+        self.loop.run_until_complete(macro.run())
         self.assertListEqual(self.result, [
-            ('r', 1), ('r', 0),
-            ('-', 1), ('-', 0),
-            ('r', 1), ('r', 0),
-            ('-', 1), ('-', 0),
-            ('m', 1), ('m', 0),
+            (r, 1), (r, 0),
+            (minus, 1), (minus, 0),
+            (r, 1), (r, 0),
+            (minus, 1), (minus, 0),
+            (m, 1), (m, 0),
         ])
 
     def test_5(self):
         start = time.time()
-        macro = 'w(200).r(2,m(w,\nr(2,\tk(r))).w(10).k(k))'
-        self.loop.run_until_complete(parse(macro, self.handler).run())
+        macro = parse('w(200).r(2,m(w,\nr(2,\tk(BtN_LeFt))).w(10).k(k))')
+        macro.set_handler(self.handler)
+
+        w = system_mapping.get('w')
+        left = system_mapping.get('bTn_lEfT')
+        k = system_mapping.get('k')
+
+        self.assertSetEqual(macro.get_capabilities(), {w, left, k})
+
+        self.loop.run_until_complete(macro.run())
 
         num_pauses = 8 + 6 + 4
         keystroke_time = num_pauses * config.get('macros.keystroke_sleep_ms')
@@ -103,17 +152,18 @@ class TestMacros(unittest.TestCase):
 
         self.assertLess(time.time() - start, total_time * 1.1)
         self.assertGreater(time.time() - start, total_time * 0.9)
-        expected = [('w', 1)]
-        expected += [('r', 1), ('r', 0)] * 2
-        expected += [('w', 0)]
-        expected += [('k', 1), ('k', 0)]
+        expected = [(w, 1)]
+        expected += [(left, 1), (left, 0)] * 2
+        expected += [(w, 0)]
+        expected += [(k, 1), (k, 0)]
         expected *= 2
         self.assertListEqual(self.result, expected)
 
     def test_6(self):
         # does nothing without .run
-        ret = parse('k(a).r(3, k(b))', self.handler)
-        self.assertIsInstance(ret, _Macro)
+        macro = parse('k(a).r(3, k(b))')
+        macro.set_handler(self.handler)
+        self.assertIsInstance(macro, _Macro)
         self.assertListEqual(self.result, [])
 
 
diff --git a/tests/testcases/test_mapping.py b/tests/testcases/test_mapping.py
index b9ad39e1..7f22d65a 100644
--- a/tests/testcases/test_mapping.py
+++ b/tests/testcases/test_mapping.py
@@ -23,7 +23,7 @@ import unittest
 from evdev.events import EV_KEY, EV_ABS
 
 from keymapper.mapping import Mapping
-from keymapper.state import populate_system_mapping
+from keymapper.state import SystemMapping
 
 
 class TestMapping(unittest.TestCase):
@@ -31,18 +31,28 @@ class TestMapping(unittest.TestCase):
         self.mapping = Mapping()
         self.assertFalse(self.mapping.changed)
 
-    def test_populate_system_mapping(self):
-        # not actually a mapping object, just a dict
-        mapping = populate_system_mapping()
-        self.assertGreater(len(mapping), 100)
-        self.assertEqual(mapping['1'], 2)
-        self.assertEqual(mapping['KEY_1'], 2)
+    def test_system_mapping(self):
+        system_mapping = SystemMapping()
+        self.assertGreater(len(system_mapping._mapping), 100)
+        self.assertEqual(system_mapping.get('1'), 2)
+        self.assertEqual(system_mapping.get('KeY_1'), 2)
 
-        self.assertEqual(mapping['Alt_L'], 56)
-        self.assertEqual(mapping['KEY_LEFTALT'], 56)
+        self.assertEqual(system_mapping.get('AlT_L'), 56)
+        self.assertEqual(system_mapping.get('KEy_LEFtALT'), 56)
 
-        self.assertEqual(mapping['KEY_LEFTSHIFT'], 42)
-        self.assertEqual(mapping['Shift_L'], 42)
+        self.assertEqual(system_mapping.get('kEY_LeFTSHIFT'), 42)
+        self.assertEqual(system_mapping.get('ShiFt_L'), 42)
+
+        self.assertIsNotNone(system_mapping.get('kp_1'))
+        self.assertIsNotNone(system_mapping.get('KP_1'))
+        self.assertEqual(
+            system_mapping.get('KP_Left'),
+            system_mapping.get('KP_4')
+        )
+        self.assertEqual(
+            system_mapping.get('KP_Left'),
+            system_mapping.get('KEY_KP4')
+        )
 
     def test_clone(self):
         mapping1 = Mapping()